U.S. patent application number 17/293205 was filed with the patent office on 2022-01-13 for optical lens having an interferential coating and a multilayer system for improving abrasion-resistance.
The applicant listed for this patent is Essilor International. Invention is credited to Xingzhao DING, Frederic GUILLAIN, William TROTTIER-LAPOINTE, Christophe VALENTI.
Application Number | 20220011600 17/293205 |
Document ID | / |
Family ID | |
Filed Date | 2022-01-13 |
United States Patent
Application |
20220011600 |
Kind Code |
A1 |
VALENTI; Christophe ; et
al. |
January 13, 2022 |
Optical Lens Having an Interferential Coating and a Multilayer
System for Improving Abrasion-Resistance
Abstract
The invention relates to an optical lens comprising a substrate
having a front main face and a rear main face, at least one main
face of which being successively coated with a first high
refractive index sheet which does not comprise any Ta.sub.2O.sub.5
layer, a second low refractive index sheet a third high refractive
index sheet, a monolayer sub-layer having a thickness higher than
or equal 0 to 100 nm, and a multilayer interferential coating
comprising a stack of at least one high refractive index layer and
at least one low refractive index layer. The mean reflection factor
R.sub.UV on said rear main face between 280 nm and 380 nm, weighted
by the function W(.lamda.) defined in the ISO 13666:1998 standard,
is lower than 10%, for an angle of incidence of 35.degree. .20
Inventors: |
VALENTI; Christophe;
(Charenton-le-Pont, FR) ; GUILLAIN; Frederic;
(Charenton-le-Pont, FR) ; TROTTIER-LAPOINTE; William;
(Charenton-le-Pont, FR) ; DING; Xingzhao;
(Singapore, SG) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Essilor International |
Charenton-le-Pont |
|
FR |
|
|
Appl. No.: |
17/293205 |
Filed: |
November 18, 2019 |
PCT Filed: |
November 18, 2019 |
PCT NO: |
PCT/EP2019/081685 |
371 Date: |
May 12, 2021 |
International
Class: |
G02C 7/10 20060101
G02C007/10; G02B 5/28 20060101 G02B005/28; G02C 7/02 20060101
G02C007/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 19, 2018 |
EP |
18306519.2 |
Claims
1.-15. (canceled)
16. An optical lens comprising: a substrate having a front main
face and a rear main face, at least one main face of which being
successively coated with: (A) a first high refractive index sheet
having a refractive index higher than 1.55, which does not comprise
any Ta.sub.2O.sub.5 layer; (B) a second low refractive index sheet
having a refractive index of 1.55 or less in direct contact with
the former sheet; (C) a third high refractive index sheet having a
refractive index higher than 1.55 in direct contact with the former
sheet; a monolayer sub-layer having a thickness higher than or
equal to 100 nm in direct contact with the former sheet (C); a
multilayer interferential coating comprising a stack of at least
one high refractive index layer having a refractive index higher
than 1.55 and at least one low refractive index layer having a
refractive index of 1.55 or less; and the mean reflection factor
R.sub.UV on said rear main face between 280 nm and 380 nm, weighted
by the function W(.lamda.) defined in the ISO 13666: 1998 standard,
is lower than 10%, for an angle of incidence of 35.degree..
17. The optical lens of claim 16, wherein the sub-layer has a
thickness higher than or equal to 120 nm.
18. The optical lens of claim 16, wherein the deposition of said
sub-layer is performed in a vacuum chamber in which no
supplementary gas is supplied during said deposition.
19. The optical lens of claim 16, wherein the sub-layer is a
SiO.sub.2-based layer.
20. The optical lens of claim 16, wherein the interferential
coating comprises at least one Ta.sub.2O.sub.5-based layer.
21. The optical lens of claim 16, wherein the interferential
coating comprises at least one electrically conductive layer.
22. The optical lens of claim 16, wherein the interferential
coating comprises at least one electrically conductive layer, which
is a SnO.sub.2 based layer.
23. The optical lens of claim 16, wherein the interferential
coating is an anti-reflection coating.
24. The optical lens of claim 16, wherein the optical lens is an
ophthalmic lens.
25. The optical lens of claim 16, wherein the first high refractive
index sheet (A) having a refractive index higher than 1.55 is a
ZrO.sub.2-based layer.
26. The optical lens of claim 16, wherein the second low refractive
index sheet (B) having a refractive index of 1.55 or less is a
SiO.sub.2-based layer.
27. The optical lens of claim 16, wherein the third high refractive
index sheet (C) having a refractive index higher than 1.55
comprises at least one material selected from Ta.sub.2O.sub.5,
Nb.sub.2O.sub.5, PrTiO.sub.3, ZrO.sub.2 and Y.sub.2O.sub.3.
28. The optical lens of claim 16, wherein the ratio: R T .times.
.times. 1 = sum .times. .times. of .times. .times. the .times.
.times. physical .times. .times. thicknesses .times. .times. of
.times. .times. the .times. .times. low .times. .times. refractive
index .times. .times. layers .times. .times. of .times. .times. the
.times. .times. interferential .times. .times. coating sum .times.
.times. of .times. .times. the .times. .times. physical .times.
.times. thicknesses .times. .times. of .times. .times. the .times.
.times. high .times. .times. refractive index .times. .times.
layers .times. .times. of .times. .times. the .times. .times.
interferential .times. .times. coating ##EQU00003## is higher than
or equal to 0.8.
29. The optical lens of claim 16, wherein the ratio: R T .times.
.times. 1 = sum .times. .times. of .times. .times. the .times.
.times. physical .times. .times. thicknesses .times. .times. of
.times. .times. the .times. .times. low .times. .times. refractive
index .times. .times. layers .times. .times. of .times. .times. the
.times. .times. interferential .times. .times. coating sum .times.
.times. of .times. .times. the .times. .times. physical .times.
.times. thicknesses .times. .times. of .times. .times. the .times.
.times. high .times. .times. refractive index .times. .times.
layers .times. .times. of .times. .times. the .times. .times.
interferential .times. .times. coating ##EQU00004## is higher than
or equal to 1.5.
30. The optical lens of claim 16, wherein the thickness of said
second low refractive index sheet (B) having a refractive index of
1.55 or less is lower than or equal to 80 nm.
31. The optical lens of claim 16, wherein the thickness of said
second low refractive index sheet (B) having a refractive index of
1.55 or less is lower than or equal to 60 nm.
32. The optical lens of claim 16, wherein the first high refractive
index sheet (A) having a refractive index higher than 1.55 and the
third high refractive index sheet (C) having a refractive index
higher than 1.55 have a thickness lower than or equal to 60 nm.
33. The optical lens of claim 16, wherein the first high refractive
index sheet (A) having a refractive index higher than 1.55 and the
third high refractive index sheet (C) having a refractive index
higher than 1.55 have a thickness lower than or equal to 25 nm.
34. The optical lens of claim 16, wherein the first high refractive
index sheet (A) having a refractive index higher than 1.55 is
deposited on an abrasion and/or scratch resistant coating, and said
at least one main face of the substrate is the rear face.
35. A method of manufacturing the optical lens of claim 16,
comprising: providing an optical lens comprising a substrate having
a front main face and a rear main face; depositing onto at least
one main face of the substrate, in this order, a first high
refractive index sheet (A) having a refractive index higher than
1.55, which does not comprise any Ta.sub.2O.sub.5 layer, a second
low refractive index sheet (B) having a refractive index of 1.55 or
less so that it is in direct contact with the former sheet (A), a
third high refractive index sheet (C) having a refractive index
higher than 1.55 so that it is in direct contact with the former
sheet (B), a monolayer sub-layer having a thickness higher than or
equal to 100 nm so that it is in direct contact with the former
sheet (C), and a multilayer interferential coating comprising a
stack of at least one high refractive index layer having a
refractive index higher than 1.55 and at least one low refractive
index layer having a refractive index of 1.55 or less; wherein the
mean reflection factor R.sub.UV on said rear main face between 280
nm and 380 nm, weighted by the function W(.lamda.) defined in the
ISO 13666: 1998 standard, is lower than 10%, for an angle of
incidence of 35.degree..
Description
[0001] The invention relates to an optical article comprising a
substrate coated with a multilayer transparent interferential
coating, typically an antireflection coating, having an improved
abrasion resistance and good thermal resistance, in particular an
ophthalmic lens, and a method of manufacturing such optical
article.
[0002] It is a common practice in the art to coat at least one main
surface of an optical substrate with several coatings for imparting
to the finished article additional or improved optical or
mechanical properties. These coatings are designated in general as
functional coatings.
[0003] The various coatings that may be used to impart a plurality
of mechanical and/or optical properties may be impact-resistant
coating layers, abrasion- and/or scratch-resistant coating layers,
anti-reflection and/or reflective coating layers, and/or
anti-fouling layers and/or anti-fog layers.
[0004] Different ways to improve the abrasion resistance of an
optical article, which is sensitive to scratches from environment,
can be found in the literature. For instance, it has been proposed
to use a relatively thick sub-layer below the antireflection
coating, or increase the total thickness of the anti-reflection
coating, such as in JP 2003-195003 and JP 2003-294906, where a lens
coated with a primer coating, a hard coat and a 7-layer
anti-reflection coating comprising alternated layers of SiO.sub.2
and TiO.sub.2, the latter being deposited with ion assistance and
known to be sensitive to photo-degradation, is described. In JP
2003-294906, it is advised to control the film thicknesses of the
first three layers of the antireflection coating (counted from the
substrate side), and to use a high ratio of (sum of the physical
thicknesses of the SiO.sub.2 layers)/(sum of the physical
thicknesses of the TiO.sub.2 layers) calculated for the first three
layers.
[0005] U.S. Pat. No. 8,982,466 relates to an optical lens having a
hard coat and a multilayer anti-reflection coating in which the
high-refractive-index layers, made of TiO.sub.2, together have a
thickness of less than 40 nm.
[0006] EP 2775341 discloses an eyeglass lens having a hard coat
layer, a 360-390 nm thick SiO.sub.2 sub-layer and a 4-layer
interferential coating made of SiO.sub.2, ZrO.sub.2 and/or
Ta.sub.2O.sub.5, in which the layers have a specific
nanoindentation hardness and compressive stress, and have generally
been deposited by ion-assisted vapor deposition. This deposition
technique increases compressive stress and as a result may lead to
delamination.
[0007] JP 2002-122820 describes a hard-coated substrate coated with
a SiO.sub.2 sub-layer having a physical thickness of 89-178 nm
(optical thickness: 0.25-0.5 .lamda. at 520 nm) and a 4-layer
anti-reflection coating (ZrO.sub.2/SiO.sub.2/ZrO.sub.2/SiO.sub.2).
According to this document, high critical temperatures can be
reached by being able to balance coating thickness and stress
between the layers of the various materials. However, the only
parameter which was studied was the thickness of the sub-layer. Its
thickness should be such that the ratio (sum of the physical
thicknesses of the SiO.sub.2 layers, including the sub-layer)/(sum
of the physical thicknesses of the ZrO.sub.2 layers) ranges from 2
to 3. Higher ratios are said to be undesirable because the
durability of the anti-reflection coating is decreased.
[0008] U.S. Pat. No. 7,692,855 discloses an optical article having
anti-reflection properties and high thermal resistance, comprising
a substrate having at least one main face coated with a multilayer
anti-reflection coating in which the ratio of physical thickness of
low refractive index layers/high refractive index layers is
generally higher than 2.1.
[0009] US 2008/206470 relates to a process for manufacturing an
optical article having antireflection or reflective properties,
comprising a sub-layer a sub-layer and a multilayer stack. In order
to increase the abrasion resistance of the optical article, the
sub-layer has to be deposited in a vacuum chamber with an
additional gas supply during the deposition step, and the exposed
surface of the sub-layer has to be submitted to an ionic
bombardment treatment prior to depositing the multilayer stack.
[0010] WO 2018/192998 suggests the control of the thicknesses of
the layers in an interferential coating in order to increase
abrasion resistance of an optical article, i.e., the use of a ratio
of physical thickness of external low refractive index
layer(s)/external high refractive index layer(s) higher than or
equal to 2. Further, the optical article may comprise an impedance
coating to limit interference fringes. Typically, in this instance,
the impedance coating comprises, deposited in this order onto the
optionally coated substrate, a 4-50 nm-thick SiO.sub.2 layer, and a
4-15 nm-thick ZrO.sub.2 or Ta.sub.2O.sub.5layer, which is in
contact with the sub-layer.
[0011] An objective of the current invention is to provide a
transparent optical article comprising an organic or mineral glass
substrate bearing an interferential coating, preferably a lens, and
more preferably an ophthalmic lens for eyeglasses, having an
improved abrasion resistance, a good adhesion to the substrate and
a good resistance to heat and temperature variations, i.e., a high
critical temperature, which would be an alternative to already
known reflective or antireflective coated optical articles. These
properties should be obtained without decreasing the optical
performances and other mechanical performances of said article,
such as anti-reflection or reflection performances.
[0012] Another aim of this invention is to provide a process of
manufacturing the above defined article, which could be easily
integrated into the classical manufacturing chain and would avoid
heating the substrate.
[0013] The inventors have found that these objectives could be
achieved by using a specific combination of layers deposited under
a thick sub-layer of the interferential coating. This allows in
particular to boost the abrasion resistance of the optical article
without decreasing the adherence properties of the interferential
coating.
[0014] Compared to classical interferential coatings, inventive
interferential coatings have a higher abrasion resistance, a better
adherence and similar or improved critical temperature.
[0015] Thus, the present invention relates to an optical lens
comprising a substrate having a front main face and a rear main
face, at least one main face of which being successively coated
with: [0016] (A) a first high refractive index sheet having a
refractive index higher than 1.55, which does not comprise any
Ta.sub.2O.sub.5 layer, [0017] (B) a second low refractive index
sheet having a refractive index of 1.55 or less in direct contact
with the former sheet, [0018] (C) a third high refractive index
sheet having a refractive index higher than 1.55 in direct contact
with the former sheet, [0019] a monolayer sub-layer having a
thickness higher than or equal to 100 nm in direct contact with the
former sheet (C), [0020] a multilayer interferential coating
comprising a stack of at least one high refractive index layer
having a refractive index higher than 1.55 and at least one low
refractive index layer having a refractive index of 1.55 or
less,
[0021] and the mean reflection factor R.sub.UV on said rear main
face between 280 nm and 380 nm, weighted by the function W(.lamda.)
defined in the ISO 13666: 1998 standard, is lower than 10%, for an
angle of incidence of 35.degree..
[0022] The system composed of sheets (A), (B) and (C) and the
sub-layer is used herein as a mechanical and adherence system,
while the interferential coating is used as an optical system.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The terms "comprise" (and any grammatical variation thereof,
such as "comprises" and "comprising"), "have" (and any grammatical
variation thereof, such as "has" and "having"), "contain" (and any
grammatical variation thereof, such as "contains" and
"containing"), and "include" (and any grammatical variation
thereof, such as "includes" and "including") are open-ended linking
verbs. They are used to specify the presence of stated features,
integers, steps or components or groups thereof, but do not
preclude the presence or addition of one or more other features,
integers, steps or components or groups thereof. As a result, a
method, or a step in a method, that "comprises," "has," "contains,"
or "includes" one or more steps or elements possesses those one or
more steps or elements, but is not limited to possessing only those
one or more steps or elements.
[0024] Unless otherwise indicated, all numbers or expressions
referring to quantities of ingredients, ranges, reaction
conditions, etc. used herein are to be understood as modified in
all instances by the term "about."
[0025] When an optical article comprises one or more surface
coatings, the phrase "to deposit a coating or layer onto the
optical article" means that a coating or layer is deposited onto
the outermost coating of the optical article, i.e. the coating
which is the closest to the air.
[0026] A coating that is "on" a side of a lens is defined as a
coating that (a) is positioned over that side, (b) need not be in
contact with that side, i.e., one or more intervening coatings may
be disposed between that side and the coating in question (although
it is preferably in contact with that side) and (c) need not cover
that side completely.
[0027] The term "coating" is understood to mean any layer, layer
stack or film, which may be in contact with the substrate and/or
with another coating, for example a sol-gel coating or a coating
made of an organic resin. A coating may be deposited or formed
through various methods, including wet processing, gaseous
processing, and film transfer.
[0028] The term "sheet" is understood to mean a single layer
(monolayer) or a bilayer, i.e., a set of two layers in direct
contact with each other. When a high refractive index sheet (having
a refractive index higher than 1.55) has two layers, both layers
are high refractive index layers. Similarly, when a low refractive
index sheet (having a refractive index lower than or equal to 1.55)
has two layers, both layers are low refractive index layers.
[0029] In the present application, a layer based on a material is
defined as a layer comprising at least 80% by weight of said
material, more preferably at least 90% by weight of said material,
even better consisting of a layer of said material. For example, a
ZrO.sub.2-based layer comprises at least 80% by weight of
ZrO.sub.2.
[0030] The optical article prepared according to the present
invention is a transparent optical article, preferably an optical
lens or lens blank, and more preferably an ophthalmic lens or lens
blank. The optical article may be coated on its convex main face
(front side), concave main face (back/rear side), or both faces
with sheets (A) to (C), the sub-layer and the multilayer
interferential coating according to the invention, preferably on
the convex (front) main face. As used herein, the rear face of the
substrate is intended to mean the face which, when using the
article, is the nearest from the wearer's eye, in the cases of
ophthalmic lenses. It is generally a concave face. On the contrary,
the front face of the substrate is the face which, when using the
article, is the most distant from the wearer's eye. It is generally
a convex face. The optical article can also be a plano article.
[0031] Herein, the term "lens" means an organic or inorganic glass
lens, comprising a lens substrate, which may be coated with one or
more coatings of various natures.
[0032] The term "ophthalmic lens" is used to mean a lens adapted to
a spectacle frame, for example to protect the eye and/or correct
the sight. Said lens can be chosen from afocal, unifocal, bifocal,
trifocal and progressive lenses. Although ophthalmic optics is a
preferred field of the invention, it will be understood that this
invention can be applied to optical articles of other types, such
as, for example, lenses for optical instruments, in photography or
astronomy, optical sighting lenses, ocular visors, optics of
lighting systems, etc.
[0033] In the present description, unless otherwise specified, an
optical article/material is understood to be transparent when the
observation of an image through said optical article is perceived
with no significant loss of contrast, that is, when the formation
of an image through said optical article is obtained without
adversely affecting the quality of the image. This definition of
the term "transparent" can be applied to all objects qualified as
such in the description, unless otherwise specified.
[0034] A substrate, in the sense of the present invention, should
be understood to mean an uncoated substrate, and generally has two
main faces. The substrate may in particular be an optically
transparent material having the shape of an optical article, for
example an ophthalmic lens destined to be mounted in glasses. In
this context, the term "substrate" is understood to mean the base
constituent material of the optical lens and more particularly of
the ophthalmic lens. This material acts as support for a stack of
one or more coatings or layers.
[0035] The substrate may be made of mineral glass or organic glass,
preferably organic glass. The organic glasses can be either
thermoplastic materials such as polycarbonates and thermoplastic
polyurethanes or thermosetting (cross-linked) materials such as
diethylene glycol bis(allylcarbonate) polymers and copolymers (in
particular CR-39.RTM. from PPG Industries), thermosetting
polyurethanes, polythiourethanes, preferably polythiourethane
resins having a refractive index of 1.60 or 1.67, polyepoxides,
polyepisulfides, such as those having a refractive index of 1.74,
poly(meth)acrylates and copolymers based substrates, such as
substrates comprising (meth)acrylic polymers and copolymers derived
from bisphenol-A, polythio(meth)acrylates, as well as copolymers
thereof and blends thereof. Preferred materials for the lens
substrate are polycarbonates (PC), diethylene glycol
bis(allylcarbonate) polymers and substrates obtained from
thermosetting polythiourethane resins, which are marketed by the
Mitsui Toatsu Chemicals company as MR series, in particular
MR6.RTM., MR7.RTM. and MR8.RTM. resins.
[0036] The latter substrates as well as the monomers used for their
preparation are especially described in the patents U.S. Pat. Nos,
4,689,387, 4,775,733, 5,059,673, 5,087,758 and 5,191,055.
[0037] Prior to depositing sheets (A) to (C), the sub-layer, the
interferential coating or other functional coatings, the surface of
the article is usually submitted to a physical or chemical surface
activating and cleaning pre-treatment, so as to improve the
adhesion of the layer to be deposited, such as disclosed in WO
2013/013929. This pre-treatment is generally performed on the
surface of an abrasion- and/or scratch-resistant coating (hard
coat).
[0038] This pre-treatment is generally carried out under vacuum. It
may be a bombardment with energetic species, for example an ion
beam method ("Ion Pre-Cleaning" or "IPC") or an electron beam
method, a corona treatment, an ion spallation treatment, an
ultraviolet treatment or a plasma treatment under vacuum, using
typically an oxygen or an argon plasma. It may also be an acid or a
base surface treatment and/or a solvent surface treatment (using
water or an organic solvent) with or without ultrasonic treatment.
Many treatments may be combined. Thanks to these cleaning
treatments, the cleanliness of the substrate surface is
optimized.
[0039] By energetic species, it is meant species with an energy
ranging from 1 to 300 eV, preferably from 1 to 150 eV, and more
preferably from 10 to 150 eV and most preferably from 40 to 150 eV.
Energetic species may be chemical species such as ions, radicals,
or species such as photons or electrons.
[0040] The interferential coating may be virtually any
interferential coating conventionally used in the field of optics,
in particular ophthalmic optics. The interference coating may be,
in a non-limiting manner, an anti-reflection coating, a reflective
(mirror) coating such as an infrared mirror or an ultraviolet
mirror, a filter in visible spectrum such as a blue cut filter or a
blue pass filter, but is preferably an anti-reflection coating.
[0041] An anti-reflection coating is a coating, deposited on the
surface of an article, which improves the anti-reflection
properties of the final article. It reduces the reflection of light
at the article/air interface over a relatively broad portion of the
visible spectrum.
[0042] The multilayer interferential coating of the invention
comprises a stack of at least one high refractive index layer
having a refractive index higher than 1.55 and at least one low
refractive index layer having a refractive index of 1.55 or
less.
[0043] More preferably, it comprises at least two layers with a low
refractive index (LI) and at least two layers with a high
refractive index (HI). The total number of layers in the
interferential coating is preferably higher than or equal to 3,
more preferably higher than or equal to 4, and preferably lower
than or equal to 8 or 7, more preferably lower than or equal to 6,
even more preferably lower than or equal to 5, and most preferably
equal to 5 layers.
[0044] As used herein, a layer of the interferential coating (or a
layer from sheets (A), (B) or (C)) is defined as having a thickness
higher than or equal to 1 nm. Thus, any layer having a thickness
lower than 1 nm will not be considered when counting the number of
layers in the interferential coating. The sub-layer and the layers
of sheets (A) to (C) either are not considered when counting the
number of layers of the interferential coating or when indicating
its thickness.
[0045] HI layers and LI layers do not necessarily alternate with
each other in the stack, although they also may, according to one
embodiment of the invention. Two HI layers (or more) may be
deposited onto each other, as well as two LI layers (or more) may
be deposited onto each other.
[0046] In the present application, a layer of the interferential
coating is said to be a layer with a high refractive index (HI)
when its refractive index is higher than 1.55, preferably higher
than or equal to 1.6, even more preferably higher than or equal to
1.8 or 1.9 and most preferably higher than or equal to 2. Said HI
layers preferably have a refractive index lower than or equal to
2.2 or 2.1. A layer of an interferential coating is said to be a
low refractive index layer (LI) when its refractive index is lower
than or equal to 1.55, preferably lower than or equal to 1.52, more
preferably lower than or equal to 1.48 or 1.47. Said LI layer
preferably has a refractive index higher than or equal to 1.1.
[0047] The HI layer generally comprises one or more metal oxides
such as, without limitation, zirconia (ZrO.sub.2), titanium dioxide
(TiO.sub.2), alumina (Al.sub.2O.sub.3), tantalum pentoxide
(Ta.sub.2O.sub.5), neodymium oxide (Nd.sub.2O.sub.5), praseodymium
oxide (Pr.sub.2O.sub.3), praseodymium titanate (PrTiO.sub.3),
La.sub.2O.sub.3, Nb.sub.2O.sub.5, Y.sub.2O.sub.3, with the proviso
that TiO.sub.2 is not present in the outermost high refractive
index layer(s) of the interferential coating. In some aspects of
the invention, the outermost high refractive index layer(s) of the
interferential coating do(es) not comprise titanium oxide. In a
preferred embodiment, the interferential coating does not comprise
any layer comprising TiO.sub.2, or more generally, titanium oxide.
As used herein, titanium oxide is intended to mean titanium dioxide
or a substoichiometric titanium oxide (TiOx, where x<2).
Titanium oxide-containing layers are indeed sensitive to
photo-degradation.
[0048] Optionally, the HI layers may further contain silica or
other materials with a low refractive index, provided they have a
refractive index higher than 1.55 as indicated hereabove. The
preferred materials include ZrO.sub.2, PrTiO.sub.3,
Nb.sub.2O.sub.5, Ta.sub.2O.sub.5, Y.sub.2O.sub.3 and mixtures
thereof.
[0049] In one embodiment, all the high refractive index layers
(having a refractive index higher than 1.55) of the interferential
coating comprise ZrO.sub.2. In another embodiment, the
interferential coating comprises at least one Ta.sub.2O.sub.5-based
layer.
[0050] The LI layer is also well known and may comprise, without
limitation, SiO.sub.2, MgF.sub.2, or a mixture of silica and
alumina, especially silica doped with alumina, the latter
contributing to increase the interferential coating thermal
resistance. The LI layer is preferably a layer comprising at least
80% by weight of silica, more preferably at least 90% by weight of
silica, relative to the layer total weight, and even more
preferably consists in a silica layer.
[0051] Optionally, the LI layers may further contain materials with
a high refractive index, provided the refractive index of the
resulting layer is lower than or equal to 1.55.
[0052] The interferential coating external layer, i.e., its layer
that is the furthest from the substrate is generally a silica-based
layer, comprising at least 80% by weight of silica, more preferably
at least 90% by weight of silica (for example a silica layer doped
with alumina), relative to the layer total weight, and even more
preferably consists of a silica layer.
[0053] Generally, the HI and LI layers have a physical thickness
ranging from 10 to 120 nm, preferably from 20 to 110 nm.
[0054] Generally, the total thickness of the interferential coating
plus the thickness of the sub-layer plus the thickness of sheets
(A) to (C) is lower than 1 .mu.m, preferably lower than or equal to
800 nm, more preferably lower than or equal to 500 nm and even more
preferably lower than or equal to 450 nm. The interferential
coating total thickness is generally higher than 100 nm, preferably
higher than 200 nm, and preferably lower than 1 .mu.m or 500
nm.
[0055] Moreover, the optical article has a good resistance to heat
and temperature variations, i.e., a high critical temperature. In
the present patent application, the critical temperature of an
article is defined as being the temperature starting from which
cracks appear in a coating present at the surface of the substrate
(on either main face), which results in degradation of the coating,
generally the interferential coating. The critical temperature of
an article coated according to the invention is preferably
.gtoreq.70.degree. C., more preferably .gtoreq.75.degree. C.,
80.degree. C., 90.degree. C., 100.degree. C. or 110.degree. C.
[0056] It is possible to define a R.sub.T1 ratio, which is slightly
different from the R.sub.T ratio defined in U.S. Pat. No.
7,692,855:
R T .times. .times. 1 = sum .times. .times. of .times. .times. the
.times. .times. physical .times. .times. thicknesses .times.
.times. of .times. .times. the .times. .times. low .times. .times.
refractive index .times. .times. layers .times. .times. of .times.
.times. the .times. .times. interferential .times. .times. coating
sum .times. .times. of .times. .times. the .times. .times. physical
.times. .times. thicknesses .times. .times. of .times. .times. the
.times. .times. high .times. .times. refractive index .times.
.times. layers .times. .times. of .times. .times. the .times.
.times. interferential .times. .times. coating ##EQU00001##
[0057] In the present invention, only layers of the interferential
coating are taken into account for the calculation of said ratio
R.sub.T1, i.e., only the layers located above the sub-layer.
[0058] In one embodiment R.sub.T1 is higher than or equal to 0.8,
preferably higher than or equal to 1, 1.3, 1.5, 1.9, 2, 2.1, 2.2 or
2.5. In one embodiment, R.sub.T1 is lower than 5, preferably lower
than at least one of the following values 4, 3.5, 3. In another
embodiment, R.sub.T1 ranges from 0.8 to 2.5. It is preferable to
have a high R.sub.T1 ratio, in order to have an article showing a
higher critical temperature, while exhibiting in the same time high
abrasion resistance.
[0059] In the present invention, the multilayer interferential
coating is deposited onto a monolayer sub-layer having a thickness
higher than or equal to 100 nm. It should be noted that such
sub-layer does not belong to the interferential coating. Said
sub-layer in preferably in direct contact with the interferential
coating.
[0060] As used herein, an interferential coating sub-layer or
adhesion layer is intended to mean a relatively thick coating, used
in order to improve mechanical properties such as abrasion
resistance and/or scratch resistance of the interferential coating
and/or so as to reinforce its adhesion to the substrate or to the
underlying coating.
[0061] The sub-layer has a thickness that is generally lower than
or equal to any one of the following values: 600 nm, 500 nm, 450
nm, 400 nm, 375 nm, and that is generally higher than or equal to
110 nm, more preferably higher than or equal to 120, 130, 140, 150,
160 or 180 nm. Increasing the thickness of the sub-layer leads to
an abrasion resistance improvement.
[0062] The sub-layer is preferably a SiO.sub.2-based layer, this
layer comprising preferably at least 80% by weight of silica, more
preferably at least 90% by weight of silica, relative to the layer
total weight, and even more preferably consists of a silica layer.
In another embodiment, this SiO.sub.2-based layer is a silica layer
doped with alumina, in amounts such as defined hereabove,
preferably consists of a silica layer doped with alumina.
[0063] In the present invention, the monolayer sub-layer is
deposited onto a system of three sheets (A), (B) and (C), deposited
in this order onto the optionally coated substrate. It should be
noted that such sheets do not belong to the interferential coating.
Said sub-layer is in direct contact with sheet (C). This system
allows to improve abrasion resistance of the optical article
without suffering from adhesion issues between the sub-layer and
the underlying coating or the substrate.
[0064] Indeed, adhesion problems can be observed due to mechanical
stresses when some means are implemented to improve the abrasion
resistance of the optical article, such as increasing the thickness
of the sub-layer and/or depositing the sub-layer under a low
pressure, preferably without additional gas supply, so as to
increase its compression/density.
[0065] The first high refractive index sheet (A), having a
refractive index higher than 1.55, does not comprise any
Ta.sub.2O.sub.5 layer and preferably does not comprise any
Ta.sub.2O.sub.5-based layer. Sheet (A) may comprise one single high
refractive index layer or two high refractive index layers in
direct contact. The layer(s) of sheet (A) generally comprise(s) one
or more metal oxides, which can be chosen from the metal oxides
previously described for the high refractive index layers of the
interferential coating. Ta.sub.2O.sub.5 can be present, but in an
amount of preferably less than 80% by weight, more preferably less
than 75%, 50%, 25%, 10%, 5%, or 1% by weight. In one embodiment, no
layer of sheet (A) comprises Ta.sub.2O5.
[0066] Sheet (A) preferably comprises a ZrO.sub.2-based layer, more
preferably is a ZrO.sub.2-based layer. In one embodiment, sheet (A)
comprises a ZrO.sub.2 layer, more preferably is a ZrO.sub.2
layer.
[0067] Sheet (A) preferably has a thickness lower than or equal to
60 nm, more preferably lower than or equal to 50 nm, 40 nm, 30 nm,
25 nm, 20 nm or 15 nm. Sheet (A) preferably has a thickness higher
than or equal to 4 nm, more preferably higher than or equal to 5 nm
or 7 nm.
[0068] In one embodiment, sheet (A) comprises a high refractive
index silicon-organic layer such as disclosed in WO 2017/021669,
obtained by vacuum deposition, assisted by a source of ions, of at
least one metal oxide and at least one organosilicon compound, such
as octamethylcyclotetrasiloxane, decamethyltetrasiloxane,
2,4,6,8-tetramethylcyclotetrasiloxane, hexamethyldisiloxane,
decamethylcyclopentasiloxane or dodecamethylpentasiloxane, said
layer containing at least one metal oxide having a refractive index
higher than or equal to 1.8, such as ZrO.sub.2.
[0069] In one embodiment, sheet (A) comprises two high refractive
index layers in direct contact and its high refractive index layer
in direct contact with the optionally coated substrate is an
adhesion layer. Said adhesion layer may comprise a metal or metal
oxide selected from chromium; sub-stoichiometric silicon oxide SiOx
with 0.5<x<1.5, preferably 0.9<x<1.1 so as to have a
refractive index larger than 1.55; and a mixture comprising
chromium, silicon and oxygen, preferably chromium and silicon
oxide(s) in which silicon oxides represent from 50 to 95% by
weight, preferably from 65 to 92% by weight of said layer. Examples
of commercially available materials that can be used to form said
adhesion layer comprising chromium, silicon and oxygen are the
materials Malbunit 8/1 (mixture of SiO.sub.2 and Cr) and Flexo
(mixture of SiO and Cr), provided by the Umicore Materials AG
company. In this embodiment, adhesion between sheet (A) and
underlying optionally coated substrate is improved and delamination
occurrence (adhesive failure) is decreased.
[0070] The second low refractive index sheet (B), having a
refractive index of 1.55 or less, is in direct contact with sheet
(A). Sheet (B) may comprise one single low refractive index layer
or two low refractive index layers in direct contact. The layer(s)
of sheet (B) generally comprise(s) one or more metal oxides, which
can be chosen from the metal oxides previously described for the
low refractive index layers of the interferential coating.
[0071] Sheet (B) preferably comprises a SiO.sub.2-based layer, more
preferably is a SiO.sub.2-based layer. In one embodiment, sheet (B)
comprises a SiO.sub.2 layer, more preferably is a SiO.sub.2
layer.
[0072] In one embodiment, sheet (B) comprises a low refractive
index silicon-organic layer such as disclosed in WO 2017/021669,
obtained by vacuum deposition, assisted by a source of ions, of at
least one organosilicon compound such as
octamethylcyclotetrasiloxane, decamethyltetrasiloxane,
2,4,6,8-tetramethylcyclotetrasiloxane, hexamethyldisiloxane,
decamethylcyclopentasiloxane or dodecamethylpentasiloxane.
[0073] Sheet (B) preferably has a thickness lower than or equal to
80 nm, more preferably lower than or equal to 75 nm, 70 nm, 65 nm,
60 nm or 55 nm. Sheet (B) preferably has a thickness higher than or
equal to 20 nm, more preferably higher than or equal to 25 nm, 30
nm or 35 nm. Having a sufficiently thick sheet (B) is important for
obtaining an improved abrasion resistance.
[0074] The thickness of sheet (B) is preferably lower than or equal
to 60 nm or 55 nm when sheet (A) is in direct contact with an
uncoated substrate having a refractive index of 1.55 or more or is
in direct contact with a coating (typically an abrasion and/or
scratch resistant coating) having a refractive index of 1.55 or
more.
[0075] In one embodiment, the deposition of the layers of sheet (B)
is performed in a vacuum chamber in which no supplementary gas is
supplied during said deposition, which increases its density.
[0076] The third high refractive index sheet (C), having a
refractive index higher than 1.55, is in direct contact with sheet
(B). Sheet (C) may comprise one single high refractive index layer
or two high refractive index layers in direct contact. The layer(s)
of sheet (C) generally comprise(s) one or more metal oxides, which
can be chosen from the metal oxides previously described for the
high refractive index layers of the interferential coating, such as
Ta.sub.2O.sub.5, Nb.sub.2O.sub.5, PrTiO.sub.3, ZrO.sub.2 and
Y.sub.2O.sub.3.
[0077] In one embodiment, sheet (C) does not comprise any
Ta.sub.2O.sub.5 layer, preferably any Ta.sub.2O.sub.5-based layer.
In another embodiment, Ta.sub.2O.sub.5 is present in a layer of
sheet (C) in an amount of less than 80% by weight, preferably less
than 75%, 50%, 25%, 10%, 5%, or 1% by weight. In one embodiment, no
layer of sheet (C) comprises Ta.sub.2O.sub.5.
[0078] Sheet (C) preferably comprises a ZrO.sub.2-based layer, more
preferably is a ZrO.sub.2-based layer. In one embodiment, sheet (C)
comprises a ZrO.sub.2 layer, more preferably is a ZrO.sub.2
layer.
[0079] Sheet (C) preferably has a thickness lower than or equal to
60 nm, more preferably lower than or equal to 50 nm, 40 nm, 30 nm,
25 nm, 20 nm or 15 nm. In one embodiment, these thickness
requirements are simultaneously satisfied by sheets (A) and (C).
Sheet (A) preferably has a thickness higher than or equal to 4 nm,
more preferably higher than or equal to 5 nm, 7 nm or 10 nm.
[0080] In one embodiment, sheet (C) comprises a high refractive
index silicon-organic layer such as disclosed in WO 2017/021669,
obtained by vacuum deposition, assisted by a source of ions, of at
least one metal oxide and at least one organosilicon compound, such
as octamethylcyclotetrasiloxane, decamethyltetrasiloxane,
2,4,6,8-tetramethylcyclotetrasiloxane, hexamethyldisiloxane,
decamethylcyclopentasiloxane or dodecamethylpentasiloxane, said
layer containing at least one metal oxide having a refractive index
higher than or equal to 1.8, such as ZrO.sub.2.
[0081] The total thickness of sheets (A), (B) and (C) preferably
ranges from 40 to 100 nm, more preferably from 45 to 80 nm or from
50 to 75 nm.
[0082] The refractive indexes of sheets (A) and (C) can be
independently chosen from the refractive indexes previously
described for the high refractive index layers of the
interferential coating. The refractive index of sheet (B) can be
chosen from the refractive indexes previously described for the low
refractive index layers of the interferential coating.
[0083] The total number of layers of the system of sheets (A) to
(C) ranges from 3 to 6, more preferably from 3 to 4 or 5, and is
ideally equal to three. In other words, sheets (A) and/or (B)
and/or (C) are preferably monolayers. This system preferably
comprises, in the direction moving away from the substrate, a
ZrO.sub.2-based layer, a SiO.sub.2-based layer, and a
ZrO.sub.2-based layer, more preferably consists of a
ZrO.sub.2-based layer, a SiO.sub.2-based layer, and a
ZrO.sub.2-based layer. This system preferably comprises, in the
direction moving away from the substrate, a ZrO.sub.2 layer, a
SiO.sub.2 layer, and a ZrO.sub.2 layer, more preferably consists of
a ZrO.sub.2 layer, a SiO.sub.2 layer, and a ZrO.sub.2 layer.
[0084] Optionally, the exposed surface of the sub-layer may be
submitted, prior to depositing the first layer of the
interferential coating, to a physical or a chemical activation
treatment which may be selected from the pre-treatments the
substrate may undergo prior to depositing the sub-layer and which
have already been mentioned hereabove. The preferred pre-treatment
is an ion bombardment, for example by using an ion gun-generated
argon ion beam. Such physical or chemical activation treatments
(preferably an ionic bombardment treatment) may also be performed
on the exposed surface of one or more layer(s) of the multilayer
interference coating, prior to depositing the subsequent layer of
said multilayer interferential coating.
[0085] The optical article of the invention may be made antistatic,
that is to say not to retain and/or develop a substantial static
charge, by incorporating at least one electrically conductive layer
into the stack present on the surface of the article, preferably in
the interferential coating.
[0086] The ability for a lens to evacuate a static charge obtained
after rubbing with a piece of cloth or using any other procedure to
generate a static charge (charge applied by corona . . . ) may be
quantified by measuring the time it takes for said charge to
dissipate. Thus, antistatic lenses have a discharge time of about a
few hundred milliseconds, preferably 500 ms or less, whereas it is
of about several tens of seconds for a static lens. In the present
application, discharge times are measured according to the method
exposed in the French application FR 2943798.
[0087] As used herein, an "electrically conductive layer" or an
"antistatic layer" is intended to mean a layer which, due to its
presence on the surface of a substrate, decreases the ability of
the optical article to attract dust/particles due to charge
accumulation. Preferably, when applied onto a non-antistatic
substrate (i.e. having a discharge time higher than 500 ms), the
antistatic layer enables the optical article not to retain and/or
develop a substantial static charge, for example to have a
discharge time of 500 ms or less after a static charge has been
applied onto the surface thereof, so that small dust is prevented
from adhering to the optical article due to prevention of static
effects.
[0088] The electrically conductive layer may be located at various
places in the stack, generally in or in contact with the
interferential coating, provided that the reflective or
anti-reflective properties thereof are not affected. It is
preferably located between two layers of the interferential
coating, and/or is preferably adjacent to a layer with a high
refractive index of such interferential coating. In an embodiment,
the electrically conductive layer is located immediately under a
layer with a low refractive index of the interferential coating,
most preferably is the penultimate layer of the interferential
coating by being located immediately under the LI external layer of
the interferential coating.
[0089] In one embodiment, the electrically conductive layer is in
direct contact with two layers having a refractive index of 1.55 or
less, and said electrically conductive layer is preferably located
in penultimate position of the interferential coating in the
direction moving away from the substrate.
[0090] The electrically conductive layer should be thin enough not
to alter the transparency of the interferential coating. The
electrically conductive layer is preferably made from an
electrically conductive and highly transparent material, generally
an optionally doped metal oxide. In this case, the thickness
thereof preferably ranges from 1 to 15 nm, more preferably from 1
to 10 nm, ideally from 2 to 8 nm. Preferably, the electrically
conductive layer comprises an optionally doped metal oxide,
selected from indium, tin, zinc oxides and mixtures thereof.
Tin-indium oxide (In.sub.2O.sub.3:Sn, tin-doped indium oxide),
aluminum-doped zinc oxide (ZnO:Al), indium oxide (In.sub.2O.sub.3)
and tin oxide (SnO.sub.2) are preferred. In a most preferred
embodiment, the electrically conductive and optically transparent
layer is a tin-indium oxide layer, noted ITO layer or a tin oxide
layer.
[0091] Generally, the electrically conductive layer contributes,
within the stack, but in a limited manner because of its low
thickness, to obtaining interferential properties and typically
represents a layer with a high refractive index in said coating.
This is the case for those layers made from an electrically
conductive and highly transparent material such as ITO or SnO.sub.2
layers. Accordingly, when it is present, the electrically
conductive layer is preferably the outermost high refractive index
layer of the interferential coating, or one of the outermost high
refractive index layers of the interferential coating when it is
adjacent to one or more high refractive index layers.
[0092] The electrically conductive layer may be deposited according
to any suitable method, for example by vacuum evaporation
deposition, preferably ion-beam-assisted (IAD, described below) to
increase its transparence, or by means of cathode sputtering.
[0093] The electrically conductive layer may also be a very thin
layer of a noble metal (Ag, Au, Pt, etc.) typically smaller than 1
nm in thickness and preferably less than 0.5 nm in thickness.
[0094] The various layers of the interferential coating, the
sub-layer, and sheets (A) to (C) are preferably deposited by vapor
phase deposition, under vacuum, according to any of the following
methods: i) by evaporation, optionally under ion beam assistance;
ii) by ion-beam spraying; iii) by cathode sputtering; iv) by
plasma-assisted chemical vapor deposition. These various methods
are described in the following references "Thin Film Processes" and
"Thin Film Processes II," Vossen & Kern, Ed., Academic Press,
1978 and 1991, respectively. A particularly recommended method is
evaporation under vacuum. Preferably, the deposition of each of the
above-mentioned layers is conducted by evaporation under vacuum.
Such a process does advantageously avoid heating the substrate,
which is particularly interesting for coating heat-sensitive
substrates such as organic glasses.
[0095] A treatment step with energetic species such as previously
defined may also be carried out, simultaneously whilst depositing
one or more of the various layers of the interference coating,
sub-layer, or sheets (A) to (C). In particular, working under ion
assistance enables to pack said layers while they are being formed,
and increases their compression and refractive index. The use of
ion assistance during the deposition of a layer produces a layer
that is structurally different from a layer deposited without ion
assistance.
[0096] The ion assisted deposition method or IAD is notably
described in US patent application 2006/017011 and in U.S. Pat. No.
5,268,781. Vapor phase deposition under ion assistance comprises
depositing onto a substrate a layer of material by simultaneously
bombarding by means of an ion beam said layer while it is being
formed, and preferably under ion bombardment achieved by means of
an ion gun. The ion bombardment leads to an atomic rearrangement in
the coating being formed, which increases its density. The IAD not
only allows an improvement of the deposited layer adhesion, but
also an increase in their refractive index. The IAD operation may
be performed by means of an ion gun, where ions are particles
composed of gas atoms from which one or more electron(s) is or are
extracted. It does preferably consist of bombarding the surface to
be treated with oxygen ions. Other ionized gases may be used,
either combined with oxygen, or not, for example argon, nitrogen,
in particular a mixture of O.sub.2 and argon according to a volume
ratio ranging from 2:1 to 1:2.
[0097] The outermost low refractive index layer(s) of the
interferential coating is (are) preferably deposited without ionic
assistance, preferably without concomitant treatment with energetic
species. In another embodiment, the low refractive index layers of
the interferential coating and/or the sub-layer are (is) deposited
without ionic assistance, preferably without concomitant treatment
with energetic species.
[0098] In one embodiment, no layer of the interferential coating is
deposited under ion assistance (preferably no layer of the
interferential coating is deposited under concomitant treatment
with energetic species), except the electrically conductive
layer(s), if present in the interferential coating.
[0099] In another embodiment, at least one HI layer of the
interferential coating is deposited under ion assistance, such as
an electrically conductive layer or a Ta.sub.2O.sub.5 layer, if
present in the interferential coating.
[0100] Optionally, the deposition of one or more of the layers is
performed by supplying (a supplementary) gas during the deposition
step of the layer in a vacuum chamber, such as disclosed in US
2008/206470. Concretely, an additional gas such as a rare gas, for
example argon, krypton, xenon, neon; a gas such as oxygen,
nitrogen, or mixtures of two gases or more amongst these, is or are
introduced into the vacuum deposition chamber while the layer is
being deposited. The gas employed during this deposition step is
not an ionized gas, more preferably not an activated gas.
[0101] This gas supply makes it possible to regulate the pressure
and differs from an ionic bombardment treatment, such as ion
assistance. It generally enables the limitation of stress in the
interferential coating and to reinforce the adhesion of the layers.
When such deposition method is used, which is called deposition
under gas pressure regulation, it is preferred to work under an
oxygen atmosphere (so called "passive oxygen"). The use of an
additional gas supply during the deposition of a layer produces a
layer that is structurally different from a layer deposited without
additional gas supply.
[0102] In an embodiment of the invention, the deposition of the
sub-layer is performed in a vacuum chamber under a pressure lower
than 1.6.times.10.sup.-4 mBar, preferably lower than 10.sup.-4
mBar, more preferably lower than 8.10.sup.-5 mBar.
[0103] In a preferred embodiment of the invention, the deposition
of the sub-layer is performed in a vacuum chamber in which no
supplementary gas is supplied during said deposition. It has been
found that depositing the sub-layer under a low pressure, and
ideally without gas supply to obtain a still lower pressure, leads
to a sub-layer with a lower porosity, a higher compression and
density, and an increase of the abrasion resistance of the optical
article.
[0104] In another embodiment, the outermost high refractive index
layer(s) of the interferential coating, except the electrically
conductive layers, if present in outermost position, is (are)
deposited in a vacuum chamber in which at least one supplementary
gas is supplied during said deposition. In another embodiment, the
high refractive index layer(s) of the interferential coating,
except the electrically conductive layer(s), if present in
outermost position, is (are) deposited in a vacuum chamber in which
at least one supplementary gas is supplied during said
deposition.
[0105] According to a particularly preferred embodiment, the
optical article comprises, starting from the surface of the
substrate optionally coated with one or more functional coatings
such as a primer coating and/or a hard coat, a high refractive
index layer (which is not a Ta.sub.2O.sub.5 layer) having a
thickness ranging from 3 to 20 nm, more preferably from 4 to 14 nm,
preferably of zirconia (sheet (A)), a low refractive index layer
having a thickness ranging from 30 to 65 nm, preferably from 35 to
60 nm, preferably of silica (sheet (B)), a high refractive index
layer having a thickness ranging from 5 to 25 nm, preferably from 6
to 21 nm, preferably of zirconia (sheet (C)), a sub-layer having a
thickness of from 100 to 300 nm, more preferably from 110 to 250
nm, even more preferably from 120 to 200 nm, preferably a
silica-based sub-layer, and an interferential coating, preferably
an anti-reflective coating, containing in the following order, a
high refractive index with a thickness of from 6 to 35 nm,
preferably of from 8 to 30 nm, preferably of zirconia or
Ta.sub.2O.sub.5, a layer with a low refractive index with a
thickness of from 15 to 50 nm, preferably of from 18 to 45 nm,
preferably of silica, a layer with a high refractive index with a
thickness of from 20 to 100 nm, preferably of from 25 to 95 nm,
preferably of zirconia or Ta.sub.2O.sub.5, optionally a layer with
a low refractive index with a thickness of from 5 to 20 nm,
preferably of from 8 to 15 nm, preferably of silica, optionally an
electrically conductive layer with a thickness of from 3 to 15 nm,
preferably of from 4 to 8 nm, preferably made of tin oxide or ITO,
and a layer with a low refractive index with a thickness of from 60
to 150 nm, preferably of from 65 to 140 nm, preferably of
silica.
[0106] The interferential coating/sub-layer/sheets (A) to (C)
system may be deposited directly onto a bare substrate. In some
applications, it is preferred that the main surface of the
substrate be coated with one or more functional coatings improving
its optical and/or mechanical properties, prior to depositing the
interferential coating of the invention. These functional coatings
traditionally used in optics may be, without limitation, an
impact-resistant primer layer, an abrasion- and/or
scratch-resistant coating (hard coat), a polarized coating, an
antistatic coating, a photochromic coating, a tinted coating or a
stack made of two or more of such coatings.
[0107] The impact-resistant primer coating which may be used in the
present invention can be any coating typically used for improving
impact resistance of a finished optical article. By definition, an
impact-resistant primer coating is a coating which improves the
impact resistance of the finished optical article as compared with
the same optical article but without the impact-resistant primer
coating.
[0108] Typical impact-resistant primer coatings are (meth)acrylic
based coatings and polyurethane based coatings. In particular, the
impact-resistant primer coating according to the invention can be
made from a latex composition such as a poly(meth)acrylic latex, a
polyurethane latex or a polyester latex.
[0109] Preferred primer compositions include compositions based on
thermoplastic polyurethanes, such as those described in the patents
JP 63-141001 and JP 63-87223, poly(meth)acrylic primer
compositions, such as those described in the patents U.S. Pat. Nos.
5,015,523 and 6,503,631, compositions based on thermosetting
polyurethanes, such as those described in the patent EP 0404111 and
compositions based on poly(meth)acrylic latexes or polyurethane
latexes, such as those described in the patents U.S. Pat. No.
5,316,791 and EP 0680492. Preferred primer compositions are
compositions based on polyurethanes and compositions based on
latexes, in particular polyurethane latexes, poly(meth)acrylic
latexes and polyester latexes, as well as their combinations. In
one embodiment, the impact-resistant primer comprises colloidal
fillers.
[0110] Poly(meth)acrylic latexes are latexes based on copolymers
essentially made of a (meth)acrylate, such as for example ethyl
(meth)acrylate, butyl (meth)acrylate, methoxyethyl (meth)acrylate
or ethoxyethyl (meth)acrylate, with at least one other co-monomer
in a typically lower amount, such as for example styrene.
[0111] Commercially available primer compositions suitable for use
in the invention include the Witcobond.RTM. 232, Witcobond.RTM.
234, Witcobond.RTM. 240, Witcobond.RTM. 242 compositions (marketed
by BAXENDEN CHEMICALS), Neorez.RTM. R-962, Neorez.RTM. R-972,
Neorez.RTM. R-986 and Neorez.RTM. R-9603 (marketed by ZENECA
RESINS), and Neocryl.RTM. A-639 (marketed by DSM coating
resins).
[0112] The thickness of the impact-resistant primer coating, after
curing, typically ranges from 0.05 to 30 .mu.m, preferably 0.2 to
20 .mu.m and more particularly from 0.5 to 10 .mu.m, and even
better 0.6 to 5 .mu.m or 0.6 to 3 .mu.m, and most preferably 0.8 to
1.5 .mu.m.
[0113] The impact-resistant primer coating is preferably in direct
contact with an abrasion- and/or scratch-resistant coating. In one
embodiment, its refractive index ranges from 1.45 to 1.55. In
another embodiment, its refractive index is higher than or equal to
1.55.
[0114] The abrasion- and/or scratch-resistant coating may be any
layer traditionally used as an anti-abrasion and/or anti-scratch
coating in the field of optical lenses.
[0115] The abrasion- and/or scratch-resistant coatings are
preferably hard coatings based on poly(meth)acrylates or silanes,
generally comprising one or more mineral fillers intended to
increase the hardness and/or the refractive index of the coating
once cured.
[0116] Abrasion- and/or scratch-resistant coatings are preferably
prepared from compositions comprising at least one alkoxysilane
and/or a hydrolyzate thereof, obtained for example through
hydrolysis with a hydrochloric acid solution and optionally
condensation and/or curing catalysts.
[0117] Suitable coatings that are recommended for the present
invention include coatings based on epoxysilane hydrolyzates such
as those described in the patents EP 0614957, U.S. Pat. Nos.
4,211,823 and 5,015,523.
[0118] A preferred abrasion- and/or scratch-resistant coating
composition is the one disclosed in the patent EP 0614957, in the
name of the applicant. It comprises a hydrolyzate of epoxy
trialkoxysilane and dialkyl dialkoxysilane, colloidal silica and a
catalytic amount of an aluminum-based curing catalyst such as
aluminum acetylacetonate, the rest being essentially composed of
solvents traditionally used for formulating such compositions.
Preferably, the hydrolyzate used is a hydrolyzate of
.gamma.-glycidoxypropyltrimethoxysilane (GLYMO) and
dimethyldiethoxysilane (DMDES).
[0119] The abrasion- and/or scratch-resistant coating composition
may be deposited by known methods and is then cured, preferably
using heat or ultraviolet radiation. The thickness of the (cured)
abrasion- and/or scratch-resistant coating does generally vary from
2 to 10 .mu.m, preferably from 3 to 5 .mu.m.
[0120] The optical article according to the invention may also
comprise coatings formed on the interferential coating and capable
of modifying the surface properties thereof, such as a hydrophobic
and/or oleophobic coating (antifouling top coat). These coatings
are preferably deposited onto the outer layer of the interferential
coating. Generally, their thickness is lower than or equal to 10
nm, does preferably range from 1 to 10 nm, more preferably from 1
to 5 nm. Antifouling top coats are generally coatings of the
fluorosilane or fluorosilazane type, preferably comprising
fluoropolyether moieties and more preferably perfluoropolyether
moieties. More detailed information on these coatings is disclosed
in WO 2012076714.
[0121] Instead of a hydrophobic coating, a hydrophilic coating may
be used which provides anti-fog properties (anti-fog coating), or a
precursor of an anti-fog coating which provides anti-fog properties
when associated with a surfactant. Examples of such anti-fog
precursor coatings are described in the patent application WO
2011/080472.
[0122] The additional coatings such as primers, hard coats and
antifouling top coats may be deposited onto a main face of the
substrate using methods known in the art, including spin-coating,
dip-coating, spray-coating, evaporation, sputtering, chemical vapor
deposition and lamination.
[0123] Typically, an optical article according to the invention
comprises a substrate that is successively coated with an
impact-resistant primer layer, an anti-abrasion and/or
scratch-resistant layer, sheets (A) to (C), a sub-layer and an
interferential coating according to the invention, and a
hydrophobic and/or oleophobic coating, or a hydrophilic coating
which provides anti-fog properties, or an anti-fog precursor
coating.
[0124] Due to the presence of sheets (A) to (C), the sub-layer and
interferential coating according to the invention (as an example an
antireflective coating), the optical articles of the invention
exhibit a high value of abrasion resistance measured according to
the Bayer ASTM (Bayer sand) operating protocol described hereafter,
i.e., in accordance with the ASTM F735-81 standard. For Bayer ASTM
measurement, the coated face has to be convex. In the examples,
when a coating is deposited on a concave face, the Bayer ASTM value
is the measurement made on the same coating (sheets (A) to (C),
sub-layer and interferential coating) but deposited on a convex
face.
[0125] According to the present invention, the optical article, the
main face of which, preferably the front face, is covered by the
interferential stack of the invention, exhibits a Bayer value
measured in accordance with the ASTM F735-81 standard (sand Bayer
value) higher than 5.5, preferably higher than any one of the
following value: 6, 6.5, 7, 7.5, 8, 9, 10, 11. Thus, the present
invention provides optical articles with a high abrasion
resistance, since typical sand Bayer values for optical articles
are around 5. Such values can be obtained by controlling the
thickness of the sub-layer and sheets (A) to (C), in particular
sheet (B), the Ru ratio, and/or the deposition parameters, in
particular the pressure during the deposition of the sub-layer.
[0126] In one embodiment, the optical article is a lens and the
interferential coating, sheets (A) to (C) and the sub-layer are
applied on the front main face of the lens and/or the rear main
face of the lens, preferably the front main face of the lens.
[0127] In another embodiment, the optical article is a lens and the
interferential coating, sheets (A) to (C) and the sub-layer are
applied on the front main face of the lens or the back main face),
and the back main face of the lens (or the front main face) is
coated with an interferential coating, preferably an antireflection
coating, which is identical to or different from the interferential
coating of the other face, optionally with a sub-layer, which is
identical to or different from the sub-layer of the other face,
optionally with sheets (A) to (C), which are identical to or
different from sheets (A) to (C) of the other face, and optionally
with an impact resistant primer coating and/or an abrasion- and/or
scratch-resistant coating, which are identical to or different from
those of the other face. Obviously, the layers of the back face are
stacked in an order that is similar to the front face.
[0128] The optical lens of the invention is configured to reduce
reflection in the UVA- and UVB-radiation ranges (respectively
315-380 nm and 280-315 nm) on the rear face, so as to allow the
best health protection against UV light.
[0129] It is advisable for a spectacle wearer to wear before each
of both eyes an ophthalmic lens that strongly reduces reflection on
the rear face in the UVA- and UVB-radiation ranges, which are
particularly harmful to the retina. Such lenses may also provide
increased visual performance due to increased contrast
sensitivity.
[0130] Reflecting UV light is not really problematic on the front
face of the lens, since the major part of the UV radiation which
comes from the front of the wearer and might attain the wearer's
eye (normal incidence, 0 to 15.degree.) generally gets absorbed by
the ophthalmic lens substrate. On the other hand, the UV radiation
resulting from light sources located behind the wearer may reflect
on the lens rear face and reach the wearer's eye if the lens is not
provided with an antireflective coating which is efficient in the
ultraviolet region, thus potentially affecting the wearer's health.
It is observed that the light rays that may reflect onto the lens
rear face and reach the wearer's eye have a narrow incidence angle
range, ranging from 30 to 45.degree. (oblique incidence).
[0131] In this regard, the mean reflection factor R.sub.UV on the
rear (back) main face of the substrate between 280 nm and 380 nm,
weighted by the function W(.lamda.) defined in the ISO 13666: 1998
standard, is preferably lower than 10% or 5%, preferably lower than
4.5%, more preferably lower than or equal to 4%, even better lower
than or equal to 3%, at an angle of incidence of 35.degree.. These
performances can be obtained through the use of an antireflection
coating deposited onto the rear main face of the lens.
[0132] The mean reflection factor R.sub.UV on the front main face
of the substrate between 280 nm and 380 nm, weighted by the
function W(.lamda.) defined in the ISO 13666: 1998 standard, is
preferably higher than 5%, preferably higher than 10%, at an angle
of incidence of 15.degree..
[0133] Said mean reflection factor R.sub.UV is defined through the
following relation:
R UV = .intg. 280 380 .times. W .function. ( .lamda. ) . R
.function. ( .lamda. ) . d .times. .times. .lamda. .intg. 380 280
.times. W .function. ( .lamda. ) . d .times. .times. .lamda.
##EQU00002##
[0134] wherein R(.lamda.) represents the lens spectral reflection
factor at a given wavelength, and W(.lamda.) represents a weighting
function equal to the product of the solar spectrum irradiance
Es(.lamda.) and the efficiency relative spectral function
S(.lamda.).
[0135] The spectral function W(.lamda.), enabling to calculate the
ultraviolet radiation transmission factors, is defined according to
the ISO 13666: 1998 standard. It makes it possible to express the
ultraviolet solar radiation distribution tempered by the relative
spectral efficiency of such radiation for a user, since it
simultaneously takes both the solar spectral energy Es(.lamda.)
into account, which does globally emit less UVB-rays as compared to
UVA-rays, and the spectral efficiency S(.lamda.), UVB-rays being
more harmful than UVA-rays. The values for those three functions in
the ultraviolet region are given in the table disclosed in ISO
13666:1998 standard (which is reproduced at page 6 of the
publication WO 2012/076714).
[0136] Ruv is measured in the present application at an angle of
incidence of 35.degree. for the back main face and at an angle of
incidence of 15.degree. for the front main face. Calculation
examples of Ruv for angles of incidence at 30.degree. and
45.degree. are given in WO 2012/076714. A person skilled in the art
can easily implement calculation based on reflection values
measured on the respective faces at the desired incidence angle
(15.degree., 35.degree.).
[0137] The "mean light reflection factor," noted R.sub.v, also
called "luminous reflection", is such as defined in the ISO 13666:
1998 standard, and measured in accordance with the ISO 8980-4
standard (for an angle of incidence lower than 17.degree.,
typically of 15.degree.), i.e. this is the weighted spectral
reflection average over the whole visible spectrum between 380 and
780 nm.
[0138] The mean light reflection factor R.sub.v of the face of the
lens coated by an anti-reflection coating according to the
invention is preferably lower than or equal to 2.5% (per face),
preferably lower than or equal to 2%, more preferably lower than or
equal to 1%, even more preferably .gtoreq.0.85%, per face of the
article.
[0139] In each of these embodiments, the total number of layers in
the interferential coating, preferably an antireflection coating,
is preferably higher than or equal to 3, preferably lower than or
equal to 5, and/or the total thickness of the interferential
coating (preferably an antireflective coating) plus the thickness
of the sub-layer plus the thickness of sheets (A) to (C) is
preferably lower than 1 micrometer, more preferably lower than or
equal to 800 nm or 500 nm.
[0140] The colorimetric coefficients C* and h of the optical
article of the invention in the international colorimetric CIE
L*a*b* are calculated between 380 and 780 nm, taking the standard
illuminant D65 and the observer into account (angle of incidence:
15.degree.). The observer is a "standard observer" (10.degree.) as
defined in the international colorimetric system CIE L*a*b*.
[0141] It is possible to prepare interferential coatings without
limitation as regards their hue angle (h), which relates to the
residual color displayed by said interferential coating (color of
the reflected light), and preferably ranges from 40.degree. to
300.degree., more preferably from 50.degree. to 290.degree.. In
some embodiments, the optical article has a hue angle (h) ranging
from 240.degree. to 300.degree., preferably from 250.degree. to
290.degree., more preferably from 260.degree. to 280.degree., thus
resulting in a perceived residual reflected color blue to violet,
preferably close to violet. In another embodiment, the optical
article has a hue angle (h) higher than or equal to 135.degree.,
more preferably higher than or equal to 140.degree. and better
ranging from 140.degree. to 160.degree., thus resulting in an
interferential coating having a green reflection. In another
embodiment, the optical article has a hue angle (h) ranging from
40.degree. to 90.degree., preferably 50.degree. to 90.degree.,
better 50.degree. to 70.degree., thus resulting in an
interferential coating having a gold reflection.
[0142] In some aspects of the invention, the interferential coating
has a chroma (C*) that is lower than 15 (for an angle of incidence
of 15.degree.), more preferably lower than 13. Obtaining low
residual color intensity (chroma) articles is preferable with
respect to wearer's comfort viewpoint, in the cases of ophthalmic
lenses.
[0143] The invention further relates to a method of manufacturing
an optical article such as described hereabove, comprising: [0144]
providing an optical lens comprising a substrate having a front
main face and a rear main face, [0145] depositing onto at least one
main face of the substrate, in this order, a first high refractive
index sheet (A) having a refractive index higher than 1.55, which
does not comprise any Ta.sub.2O.sub.5 layer, a second low
refractive index sheet (B) having a refractive index of 1.55 or
less so that it is in direct contact with the former sheet (A), a
third high refractive index sheet (C) having a refractive index
higher than 1.55 so that it is in direct contact with the former
sheet (B), a monolayer sub-layer having an exposed surface and a
thickness higher than or equal to 100 nm so that it is in direct
contact with the former sheet (C), and a multilayer interferential
coating comprising a stack of at least one high refractive index
layer having a refractive index higher than 1.55 and at least one
low refractive index layer having a refractive index of 1.55 or
less, thereby obtaining a coated optical article, wherein the mean
reflection factor R.sub.UV on said rear main face between 280 nm
and 380 nm, weighted by the function W(.lamda.) defined in the ISO
13666: 1998 standard, is lower than 10%, for an angle of incidence
of 35.degree..
[0146] In preferred embodiments, the exposed surface of the
sub-layer has been submitted to an ionic bombardment treatment
prior to depositing said multilayer interferential coating, and/or
the deposition of the sub-layer is conducted in a vacuum chamber in
which no supplementary gas is supplied during said deposition.
[0147] In another embodiment, the exposed surface of at least one
layer of the multilayer interferential coating has been submitted
to an ionic bombardment treatment prior to depositing the
subsequent layer of said multilayer interferential coating.
[0148] In another embodiment, the exposed surface of each layer of
the multilayer interferential coating except the layer of said
coating that is the furthest from the substrate has been submitted
to an ionic bombardment treatment prior to depositing the
subsequent layer of said multilayer interferential coating. This
embodiment involving multiple interlayer bombardments is preferably
implemented when the sub-layer is deposited under a low pressure
(<1.6.times.10.sup.-4 mBar or even better in a vacuum chamber
without supplying any additional gas during the deposition) to get
a better adhesion of the layers within the interferential
stack.
[0149] The exposed surface of sheet (C) is preferably submitted to
an ionic bombardment treatment prior to depositing the subsequent
layer, which is the sub-layer.
[0150] In another embodiment, the exposed surface of the following
layers is submitted to an ionic bombardment treatment prior to
depositing the subsequent layer onto said layers: sheet (C), the
sub-layer and each layer of the multilayer interferential coating
except the outermost layer of said coating.
[0151] In one embodiment, the present optical article is prepared
by forming on the substrate a primer coating and/or an abrasion-
and/or scratch-resistant coating in a first manufacturing site,
while the other coatings are formed in a second manufacturing
site.
[0152] The following examples illustrate the present invention in a
more detailed, but non-limiting manner. Unless stated otherwise,
all thicknesses disclosed in the present application relate to
physical thicknesses. The percentages given in the tables are
weight percentages. Unless otherwise specified, the refractive
indexes referred to in the present invention are expressed at
20-25.degree. C. for a wavelength of 550 nm.
EXAMPLES
1. General Procedures
[0153] The articles employed in the examples comprise a 65
mm-diameter polythiourethane MR8.RTM. lens substrate (from Mitsui
Toatsu Chemicals Inc., refractive index=1.59), with a power of
-2.00 diopters and a thickness of 1.2 mm, coated on its convex main
face with the impact resistant primer coating disclosed in the
experimental part of WO 2010/109154 modified to have a refractive
index of 1.6 by addition of high refractive index colloids, and the
abrasion- and scratch-resistant coating (hard coat) disclosed in
example 3 of EP 0614957 (modified to have a refractive index of 1.6
rather than 1.5 by adding high refractive index colloids), sheets
(A), (B) and (C), a sub-layer, an antireflection coating, and the
antifouling coating disclosed in the experimental section of patent
application WO 2010/109154, i.e., by evaporation under vacuum of
the Optool DSX.degree. compound marketed by Daikin Industries
(thickness: from 2 to 5 nm).
[0154] The concave main face of the substrate was coated with the
same impact resistant primer coating and abrasion- and
scratch-resistant coating (hard coat), and with an antireflection
coating such that the concave main face exhibits a Ruv value at an
angle of incidence of 35.degree. lower than 10%.
[0155] The various layers such as the sub-layers, sheets (A), (B)
and (C) and the layers of the antireflection coating were deposited
without heating the substrates, by vacuum evaporation, optionally
assisted (IAD) during the deposition by a beam of oxygen and
possibly argon ions, when specified (evaporation source: electron
gun), and optionally under pressure regulation by supplying
(passive) O.sub.2 gas into the chamber, where indicated.
[0156] The vacuum evaporation device that made it possible to
deposit the various antireflective layers was a vacuum coater
Syrus3 from Bulher Leybold Optics having two systems for
evaporating materials, an electron gun evaporation system, a
thermal evaporator (Joule-effect evaporation system), and a Mark 2
ion gun from Veeco for use in the preliminary phase of preparation
of the surface of the substrate by argon ion bombardment (IPC) and
in the ion-assisted deposition (IAD) of the layers.
2. Preparation of the Optical Articles
[0157] The lenses were placed on a carrousel provided with circular
openings intended to accommodate the lenses to be treated, the
concave side facing the evaporation sources and the ion gun.
[0158] The method for producing optical articles comprises
introducing the lens substrate provided with the primer and
abrasion-resistant coatings into a vacuum deposition chamber,
conducting a pumping step until a high vacuum was created, followed
by an ion gun conditioning step (IGC, such as disclosed in FR
2957454, 3.5.times.10.sup.-5 mBar as starting pressure, 140 V, 3.5
A, argon, 60 seconds), a substrate surface activation step using a
bombardment with an argon ion beam (IPC) with a starting pressure
of 5.10.sup.-4 mBar (the ion gun was set to 1.8 A, 100 V, 60
seconds), stopping the ionic irradiation, and then successively
evaporating the required number of layers (sheets (A), (B) and (C),
sub-layer, antireflection coating layers and antifouling coating)
at a rate ranging from 0.4 to 3 nm/s, and lastly a ventilation
step.
[0159] Forming an antireflection stack according to the present
invention comprises a deposition step of a ZrO.sub.2 layer (sheet
(A)) at a rate of 1 nm/s under an O.sub.2 pressure of
7.0.times.10.sup.-5 mBar, a deposition step of a SiO.sub.2 layer
(sheet (B)) at a rate of 2 nm/s, a deposition step of a ZrO.sub.2
layer (sheet (C)) at a rate of 1 nm/s under an O.sub.2 pressure of
7.0.times.10.sup.-5 mBar, a surface activation step of this
ZrO.sub.2 layer using an argon ion beam for 30 seconds (same
treatment as IPC already conducted directly on the substrate), a
deposition step of a SiO.sub.2sub-layer at a rate of 3 nm/s
optionally under an O.sub.2 atmosphere (at a pressure of
1.6.times.10.sup.-4 mBar in example 6 and comparative example 2
where O.sub.2 gas was supplied, or 5.times.10.sup.-5 mBar in the
other examples where no supplementary gas supply was performed), a
surface activation step of the sub-layer using an argon ion beam
for 30 seconds (same treatment as IPC already conducted directly on
the substrate), a deposition step of a HI layer (ZrO.sub.2 or
Ta.sub.2O.sub.5) at a rate of 2 nm/s, a deposition step of a LI
layer (SiO.sub.2) at a rate of 2 nm/s, a deposition step of a HI
layer (ZrO.sub.2 or Ta.sub.2O.sub.5) at a rate of 2 nm/s, a
deposition step of a thin electrically conductive layer (HI, ITO or
SnO.sub.2) at a rate of 1 nm/s with an oxygen ion assistance (ion
gun: 2 A, 120 V), a deposition step of a LI layer (SiO.sub.2) at a
rate of 2-3 nm/s, and lastly a deposition step of an Optool
DSX.degree.0 layer at a rate of 0.4 nm/s.
[0160] Deposition step of HI layers of ZrO.sub.2 was done with a
gas supply (O.sub.2, under a pressure of 7.5.times.10.sup.-5
mBar).
[0161] Deposition step of HI Layers of Ta.sub.2O.sub.5 was done
with an oxygen ion assistance (ion gun: 3 A, 130 V) leading to a
pressure of about 2.times.10.sup.-4 mBar.
[0162] In comparative examples 1 and 2, sheet (A) was omitted.
[0163] In comparative examples 8, sheets (A) and (B) were
omitted.
[0164] In comparative example 9, sheets (A), (B) and (C) were
omitted.
[0165] In comparative example 10, the Ta.sub.2O.sub.5 material was
used to form sheet (A).
3. Testing Methods
[0166] The following test procedures were used to evaluate the
optical articles prepared according to the present invention.
Several samples for each system were prepared for measurements and
the reported data were calculated with the average of the different
samples.
[0167] Colorimetric measurements (in reflection) of the face coated
with the stack of the invention: reflection factor Rv, hue angle h
and chroma C* in the international colorimetric CIE (L*, a*, b*)
space were carried out with a Zeiss spectrophotometer, taking into
account the standard illuminant D65, and the standard observer
10.degree. (for h and C*). They are provided for an angle of
incidence of 15.degree..
[0168] Ruv was computed from the same reflection measurement.
[0169] The critical temperature of the article was measured in the
manner indicated in patent application WO 2008/001011. It was
measured one month after production of the article.
[0170] The thickness of the layers was controlled by means of a
quartz microbalance.
[0171] Abrasion resistance was determined as disclosed in WO
2012/173596. Specifically, abrasion resistance was measured by
means of the sand Bayer test, in accordance with the ASTM F735-81
standard, 24 h after production of the article.
[0172] The adhesion properties of the whole of the interference
coating to the substrate were verified on the convex face of the
lens by means of the test commonly referred to in French as the
"n.times.10 coups" test (i.e. the "n.times.10 blows" test)
described in international patent applications WO 2010/109154 and
WO 99/49097. The test is performed in accordance with ISTM 02-011.
Briefly, a sample to be tested is placed in a clamp and covered
with a selvyt cloth impregnated with isopropyl alcohol. An eraser
positioned on a holder moving in translation is put in contact with
the cloth. The eraser is pressed down (force=60 Newtons) on the
selvyt cloth placed in contact with the lens. The test consists in
the determination, for each sample, of the number of cycles
required to cause a defect to appear in the antireflection coating.
Therefore, the higher the value obtained in the n.times.10 blows
test (average on 10 samples), the better the adhesion of the
interference coating to the optionally coated substrate, i.e.,
between sheet (A) and the underlying coating or substrate. An
article successfully passed the test if there was no defect after
20 cycles.
4. Results
[0173] The structural characteristics and the optical, mechanical
and thermo-mechanical performances of the ophthalmic lenses
obtained in the examples are detailed hereunder. The sub-layer is
gray-colored. The total thickness mentioned is the thickness of the
stack comprising the antireflection coating and the following
additional layers: sub-layer, sheets (A), (B) and (C). The stack is
deposited onto the front main face of the ophthalmic lenses when
there is no indication in the table.
[0174] Optical articles according to the invention, having sheets
(A), (B) and (C) and a sub-layer exhibit better abrasion resistance
and a better adhesion of the antireflection coating than
comparative articles (compare example 5 with comparative examples 8
and 9), while keeping a similar level of temperature resistance.
The Bayer values obtained were generally above 6, which indicates a
very high level of abrasion resistance.
[0175] It has been observed that suppression of the first high
refractive index sheet (A) led to adhesion problems at the
interface with the abrasion- and/or scratch resistant coating (data
not shown).
[0176] When the first high refractive index sheet (A) and the
second low refractive index sheet (B) are suppressed, the abrasion
resistance is lower (compare example 5 and comparative example 8).
Further, adhesion problems at the interface with the abrasion-
and/or scratch resistant coating are observed (data not shown).
[0177] When the first high refractive index sheet (A), the second
low refractive index sheet (B) and the third high refractive index
sheet (C) are suppressed, the abrasion resistance is lower, and an
adhesion failure to the substrate is observed (compare example 5
and comparative example 9). Increasing the RT1 ratio in comparative
example 12 did not restore the abrasion resistance properties.
[0178] A comparison of example 3 with example 4 shows the
beneficial effect on the abrasion resistance and critical
temperature of having a high R.sub.T1 ratio. A difference of 1.2
points is obtained in the Bayer values, which is highly
significant.
[0179] A comparison of example 5 and example 4 shows that use of
Ta.sub.2O.sub.5 rather than ZrO.sub.2 in the interferential coating
yields a slight improvement in critical temperature. Actually,
critical temperature obtained for various lenses of example 4
averages at 95.degree. C. and critical temperature obtained for
various lenses of example 5 averages at 98.degree. C. Both values
have been rounded to 100.degree. C. in tables, as critical
temperature is usually given by discrete steps of 10.degree. C. In
addition, comparison of examples 13 and 15 show than use of
Ta.sub.2O.sub.5 rather than ZrO.sub.2 in the interferential coating
yields an improvement in critical temperature.
[0180] Avoiding gas supply during deposition of the sub-layer
improved the abrasion resistance and critical temperature, but led
to adhesion problems when sheets (A) to (C) according to the
invention are not present (see comparative examples 1 and 2). These
adhesion problems were not observed in the presence of sheets (A)
to (C) according to the invention when avoiding gas supply during
deposition of the sub-layer, and the abrasion resistance and
critical temperature were still improved (compare example 5 with
example 6).
[0181] A comparison of example 5 and comparative example 10 shows
that the use of Ta.sub.2O.sub.5 rather than ZrO.sub.2 in the first
high refractive index sheet (A) and/or the third high refractive
index sheet (C) should be avoided, since this modification
significantly decreases the abrasion resistance and adhesion
properties. Further, the use of ZrO.sub.2 in the antireflection
coating provides slightly better results than the use of
Ta.sub.2O.sub.5 in terms of abrasion resistance.
[0182] Examples 13-16 are additional examples of optical articles
according to the invention, having on their concave main face
another antireflection coating with a very low reflection in the UV
range (280-380 nm).
[0183] The concave face of the optical article of example 14 was
coated with the same primer and hard coat as the convex face, and
then with the following stack (total thickness: 398 nm): SiO.sub.2
(25.7 nm)/ZrO.sub.2 (4.7 nm)/SiO.sub.2 sub-layer (160 nm, oxygen
supply during deposition: 1.2.times.10.sup.-4 mBar)/Ta.sub.2O.sub.5
(16.9 nm)/SiO.sub.2 (19.8 nm)/Ta.sub.2O.sub.5 (92.2 nm)/SnO.sub.2
(6.5 nm)/SiO.sub.2 (71.2 nm)/antifouling coating. On this concave
(back) main face, Ruv (35.degree.)=2%.
[0184] For example 15, Ruv (35.degree.)=2% on the concave (back)
main face. For example 13, Ruv (35.degree.)=2.0% on the concave
(back) main face. For example 16, Ruv (35.degree.)=2.2% on the
concave (back) main face.
* * * * *